I wonder how they are calculating "savings rate". I know I have racked up a good amount of debt up until this year because I have 1) gone to undergraduate school, 2) gone to graduate school, 3) bought a house. If you don't count my home equity in that, then yeah it looks like I wracked up MAJOR debt. My liquid Net Worth is around -$185k, but with home equity it is $140k.
A lot of people in the "Under 35" range are in school (ages 18-22 for undergrad and then 22-24 for masters if you don't graduate into unemployment for a couple years). When you are earning $20K at a part time job while going to school, -2% is only $400 a year in debt!